DCN chart, page-7

The only certain thing I can see is that CBA (or likely their client) is involved into shorting DCN.
Here is what I don't understand at all: the latest transaction (May 1) is to buy 1857043 shares in total.
The transaction before that (April 28) is "borrow increase" - borrowed from UBS. Last "borrow decrease" is dated back to 21 Apr.
One would thing that after borrowing logical thing to do is to sell short, but no, they are buying.
Can anyone explain this?